54
DMC3S - Manual - 08 - 2021
—
Overvoltage - 59
Preface
This function has two adjustable thresholds with programmable trip time.
The trip characteristic for the first threshold can be selected with definite or inverse time per IEC
60255-3/BS142.
The trip characteristic for the second threshold is definite time.
Each protection threshold can be enabled or disabled.
The first threshold can be inhibited by the start of the second threshold.
Measurement criterion
The undervoltage protection measures the fundamental component of three voltages, selected from
the three phase voltages
U
L1
,
U
L2
,
U
L3
or the three phase-to-phase voltages
U
12
,
U
23
,
U
31
, where the
latter are calculated as:
Operation and settings
Each of the three measured voltages is compared with the set thresholds (
U
>,
U
>>). The start and trip
logic for each threshold can be set to “OR” or “AND”.
When set to OR, when at least one of the three measured voltages exceeds the set threshold, the
threshold itself starts (Start) and the timer starts counting.
If the condition persists, when the operating time expires (
t
U
>,
t
U
>>), the threshold trips (Trip), other-
wise the threshold is reset.
When set to
AND
, when all three measured voltages exceed the set threshold, the threshold itself
starts (Start) and the timer starts counting.
If the condition persists, when the operating time expires (
t
U
>,
t
U
>>), the threshold trips (Trip), other-
wise the threshold is reset.
The first threshold can be set to definite or inverse time with the following characteristic curves:
t
=0.5
t
U
>
inv
/ [(
U
/
U
>
inv
) - 1]
where
t
is the operating time,
U
is the measured voltage,
U
>
inv
and
t
U
>
inv
are the set threshold and
trip time. The set operating time refers to a voltage of 1.5 times the set threshold. The minimum trip
voltage is 1.1 times the set threshold. The characteristic is defined between 1.1 and 4 times the set
threshold; if the threshold regulation exceed 0.5
U
n
, the upper limit of the measurement range is 2
U
n
.
The minimum operating time t is 0.1 s.
The definite or inverse time characteristic is selected with the parameter
U> Curve
in the menu
Set \ Protections \ Overvoltage - 59 \
Threshold U>
\ Parameters
.
Each protection threshold can be enabled or disabled by setting to
ON
or
OFF
the parameter
U>
Enable
in the menu
Set \ Protections \ Overvoltage - 59 \
Threshold U>
\ Parameters
and/or
State
in the menu
Set \ Protections \ Overvoltage - 59 \
Threshold U>> \ Definite time
.
The type of three-phase voltage measurement (phase voltage or phase-to-phase voltage), like the
protection logic (AND or OR of the three voltages), is set in the menu
Set \ Protections \ Overvoltage
- 59 \
Common configurations
, by setting parameter
Utype59;
the possible settings are
Uph-ph
(phase-to-phase) and
Uph-n
(phase).
When set to
Uph-ph
(phase-to-phase), the thresholds are expressed in p.u. Un; when set to
Uph-n
(phase), the thresholds are expressed in p.u. En.
U12=|UL1-UL2|
U23=|UL2-UL3|
U31=|UL2-UL1|
t-int-F59.ai
U
U>>
tU>
tU>>
U>
t
General characteristic of the operating time of the Overvoltage function (59)
TRIP
